Semiconductor light emitting device such as LED and LD (laser diode) are small in size and emits light of clear color efficiently. Also as semiconductor devices, they do not burn out, have good drive characteristic and are durable against vibration and repetitive operations of switching ON/OFF. For these reasons, they are used as various indicators and various light sources. However, since such semiconductor light emitting device has monochromatic peak wavelength, it has been necessary to use two or more kinds of semiconductor light emitting device to emit whitish light (white, pink or incandescent-like illumination).
In the meantime, semiconductor light emitting device made by combining LED chip that emits light of monochromatic peak wavelength and a fluorescent substance for emitting light of various colors with a single light emitting device is known as disclosed in Japanese Unexamined Patent Publication (Kokai) No. 5-152609 (Patent Document 1) and Japanese Unexamined Patent Publication (Kokai) No. 7-99345 (Patent Document 2). FIG. 4A is a schematic diagram showing an example of such a semiconductor device. Such a semiconductor light emitting device comprises an LED chip 1 that has a relatively large band gap energy in the light-emitting layer and is disposed on a cup or the like that is mounted at the distal end of a lead frame consisting of a pair of lead electrodes 7a and 7b. The LED chip 1 is electrically connected to a first lead 7a and a second lead 7b provided with the LED chip 1. A color converting member 5, containing a fluorescent substance 4 which absorbs light emitted by the LED chip and converts the wavelength of the light, is formed in contact with the LED chip 1, and a molding member 6 that covers the whole is formed adjacent to the color converting member 4.
The color converting member 4, light transmitting resin that makes the a base material for the molding member 5 and a mounting member 2 used in the semiconductor light emitting device are made of various synthetic resins in view of productivity, ease of handling and transparency. For the molding member 5, in particular, epoxy resin that is resistant to external force is preferably used. In consideration of the close contact with the molding member 5 and compatibility with the mechanical properties, the color converting member 4 provided inside is also preferably made of epoxy resin
It is proposed to use, as the epoxy resin, an epoxy resin composition which is made mainly of an alicyclic epoxy resin and is cured by an acid anhydride. The epoxy resin cured by a curing agent made of an acid anhydride is superior in light transmission properties and light resistance. For example, Unexamined Japanese Patent Publication (Kokai) No. 2000-196151 (Patent Document 3) discloses a molding resin made mainly of an alicyclic epoxy resin instead of a general bisphenol type epoxy resin. Since the epoxy resin, which is made mainly of an alicyclic epoxy resin and is cured by an acid anhydride, hardly include a carbon-carbon double bond, which can cause light deterioration, in chemical structure, deterioration of the molding resin is less likely to occur even after irradiation with light for a long time.